Image pickup tube device utilizing a magnetic field generator to reverse the leakage field

ABSTRACT

An image pickup tube device has an evacuated container including a scanning section and an image section. In the sections are respectively mounted first and second magnetic means; the former generating a magnetic field in the image section and producing a leakage of magnetic field in the other section, the latter producing a magnetic field to reverse the polarity of the leakage field.

United 1; States Patent Miyashiro et al.

[ 51 Apr. 25, 1972 IMAGE PICKUP TUBE DEVICE UTILIZING A MAGNETIC FIELDGENERATOR TO REVERSE THE LEAKAGE FIELD Inventors: Shoichi Miyashiro,Yokohama-shi; Shunzi Shirouzu, Kawasaki-shi; Mineo lwasawa,Kanagawa-ken, all of Japan Assign cc: Tokyo Shibauru Electric C0,, Ltd.,

Knwumrkiuhi, .Iupmt Filed: June [6, 1969 Appl. No.: 833,645

Foreign Application Priority Data June 20, 1968 Japan ..43/42225 u.s. Cl.315/10, 315/31 Int: Cl. ..H01J 31/26 FieldoiSearch ..3i5/l0,11,l2,3l;313/65;

250/213 R, 213 VT SOURCE OF SUPPLY SOURCE OF SUPPLY [56] ReferencesCited UNITED STATES PATENTS 3,437,867 4/1969 Miyashiro et al. ..3 1 3/79X 3,462,601 8/1969 Sternglass ...250/2l3 VT X 3,478,213 12/1969 Simon etal ..250/2 13 VT X FOREIGN PATENTS OR APPLICATIONS 664,8l3 1/1952 GreatBritain .315/10 Primary lzlt'arniner-Carl D. Quarforth AssistantExaminer-J. M. Potenza Attorney-Flynn & Frishauf [57] ABSTRACT An imagepickup tube device has an evacuated container including a scanningsection and an image section. ln the sections are respectively mountedfirst and second magnetic means; the former generating a magnetic fieldin the image section and producing a leakage of magnetic field in theother section, the latter producing a magnetic field to reverse thepolarity of the leakage field.

6 Claims, 7 Drawing Figures DEFLECTING SOURCE 24 GENERATlNG DEVICE FIG.3

D I STANCE Patented April 25, 1972 4 Sheets-Sheet 3 FIG.4

D I STANCE Patented April 25, 1972 4 Sheets-Sheet 4 IMAGEPICKUP TUBEDEVICE UTILIZING A MAGNETIC FIELD GENERATOR TO REVERSE THE LEAKAGE FIELDBACKGROUND OF THE INVENTION Thisinvention is. concerned with an imagepickup tube device. The invention is an improvement or modification ofthat disclosed in our U.S. Pat. No. 3,437,867.

In said earlier application, there is described and claimed an image.pickup tube device comprising an electron scanning section including avacuum container defining a longitudinal axis an electron gun mountedfor emitting an electron beam along said axis, focussing means forfocussing the electron beam from said electron gun, electrostatic meansfor electrostatically deflecting the focussed electron beam, cylindricalelectrode mounted coaxially with said electron. gun, a field meshelectrodefor supplying the highest electrical potential to saidelectronbeam for making said electron beam parallel to said axis, a collimationlens mounted coaxially with said electrodes andformed bytheelectrostatic field of said field mesh electrode, and a target mountedin close parallel to said field mesh electrode and scanned at a lowspeed by said electron .beam, an image section including a photoelectroncathode imounted at the otherend of said vacuum container, and amagnetictfield generator provided outside the container on saidimagesection said for focussing the image electrons from said cathode onsaid target, which produces a leakage of a maximum of 25 gauss ofmagnetic field on the axis of the containeron said target.

In the above described device, it is difficult to control a leakageofmagnetic field in the image section and cause electron beams from theelectron gun to enter the target exactly at rightangles,

SUMMARY OF THE INVENTION An image, pickup tube device comprising animage section and a scanning section, the former having a first magneticgenerating means to generate a magnetic field in said section andproduces a leakage of magnetic field in the scanning section, the latterincluding a second magnetic generating means which provides a magneticfield in said section to reverse the polarity of the leakage field(reversion of the leakage field), thereby allowing the intensity of saidleakage field to be controlled to a desired value.

, BRIEF EXPLANATION OF THE DRAWINGS FIG. 1 is a diagram illustrating animage pickup tube device according to an embodiment of this inventionapplied to an imageprthicon type pickup tube;

F [6.2 is a schematic diagram of the part near the target used inthepickup tube shown in FIG. 1;

FIG. 3 is a diagram showing the distribution of a magnetic field alongthe axis generated by the electromagnet at the part shown in FIG. 2;

FIG. 4 is a schematic diagram showing the part of a pickup tubeaccording to another embodiment of the invention, whose magneticgenerating means is a permanent magnet;

FIG. is a diagram showing the distribution of a magnetic field alongitheaxis formed by the permanent magnet shown in FIG; 4;

FIG. 16 is a diagrammatic sectional view of an intensifier vidicon inwhich the fundamental idea of the invention is applied; and FIG; 7 is adiagram showing the intensity of a magnetic field along the axis of thedevice of FIG. 6.

DESGRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, theterms listed hereinafter are construed as follows. A magnetic fieldalong the axis means a magnetic field along the longitudinal axis of theimage new that the intensity of the resultant field becomes zero interms of vector values in axial direction.

Now an image pickup tube device according to this invention as it isapplied to an image orthicon tube will be described with reference toFIG. 1.

On the internal surface of the face plate on one edge of an evacuatedcontainer 1 is provided a photoelectric cathode 2, with which coaxiallyprovided are a first cylindrical electrode 3 and a target electrode 4.At the end of the electrode 4 is mounted a disc-shaped target meshelectrode 5 in parallel to said photoelectric cathode 2, and a disctarget 6 is provided closely in parallel to said mesh electrode 5 toform an image section 7. Coaxially with the said target 6 are provided asecond cylindrical electrode 8 and a third cylindrical electrode 9. Atthe end of said second electrode 8 is mounted a field mesh electrode 10.Said mesh, second and third electrodes 8, 9 and 10 form a collimationlens 11, when the voltage is applied to these three electrodesrespectively.

On the other end of said evacuated container 1 is provided an electrongun 12, with which are coaxially mounted a fourth cylindrical electrode13, a focussing electrode 14 and a fifth electrode 15. Between saidelectrode 15 and said third electrode 9, a deflecting assembly 16 isprovided for deflecting the electron beam vertically and horizontally,in such a way that the center of deflection of said assembly 16 agreeswith the focal point of said collimation lens 11. A secondary electronmultiplier section 27 is provided around said electron gun 12 to form ascanning section 17. Said scanning section 17 and the image section 7make up an image orthicon 18. The air surrounding said orthicon 18 iscovered with an enclosure 19, whose scanning section 17 is made of amagnetic shield case 20. In the neighborhood of said photoelectriccathode 2 of the said enclosure 19 is positioned magnetic fieldgenerating device such as a solenoid coil 21 and a magnet 34, for whichcoil 21 is provided a power source 22. Further a solenoid coil 32connected to a power source 33 is accommodated in the enclosure 19 ofthe scanning section near the second electrode 8. In front of theincident light side of said photoelectron cathode 2 is provided anoptical lens 28. Around the tube 1 in the neighborhood of said electrongun 12 is disposed an alignment coil 23, which is provided with a powersource 24. Furthermore, an electric power source 25 is provided forsupplying an operation voltage for each electrode of said image orthicon18 to form an image pickup tube device 26.

Now, the operating principle of this device is explained with referenceto FIG. 1.

The various parts of an image pickup device are supplied with operatingvoltage at the following levels: 500V for the photoelectron cathode 2 ofthe image orthicon I8, -400V for the first electrode 3, 2V for thetarget electrode 4, CV for the cathode of the electron gun l2, 250V forthe fourth electrode 13, about V for the focussing electrode 14, 900Vfor the field mesh electrode 10, and 1,250V for the anode of thesecondary electron multiplier section 27. After said voltage supply, anoptical image is formed at the photoelectron cathode 2 by means of theoptical lens 28, which in turn generates image electron beams from saidcathode 2. The electron beam is electromagnetieally focussed by theaxially symmetrical magnetic field generated by the solenoid coil 21 andthe magnet 34 and by the electrical field formed by the first electrode3 and target electrode 4, and is accelerated and projected as an imageon the surface of the target 6. In this manner, the positive chargeimage is stored in said target 6.

0n the other hand, the primary electron beam 30 projected from theelectron gun 12 is focussed by the focussing electrode l4, and then isdeflected vertically and horizontally by the deflecting means 16. Thenthe primary electron beam 30 is allowed vertically to incide into thetarget 6 by the collimation lens 11 formed of the third electrode 9,second electrode 8 and field mesh electrode 10 and the axiallysymmetrical magnetic field formed by the said solenoid coils 21 and 32.At this time, the field mesh 10 of the collimation lens llflis impressedwith the highest of those voltages required in focussing the primaryelectron beam 30, and the target is supplied with a voltage of 2V.Accordingly, from the field mesh electrode to the target 6 is formed asharply decelerated electrical field, so that the primary electron beam30 impinges at a low speed on the surface of the target 6. At this time,the positive charge image stored in the target is scanned and dischargedefficiently by said primary electron beam to generate a return beamcorresponding to the positive charge image. The return electron beam 31passes through the deflecting assembly 16 and the focussing electrode 14and is led to the secondary electron multiplier section 27 where it ismultiplied to the desired value and is taken out as an output signal.

The image pickup tube described above is substantially the same type asthat disclosed in U. S. Pat. No. 3,437,865 except that there areprovided a solenoid coil 32 and power source 33 associated therewith.Accordingly, there occurs a bad effect such as a corner shading, if theintensity of a leakage magnetic field at the image section is metcontrolled to 25 gauss at maximum. The leakage field generated by themagnet 21 is distributed in one direction. Consequently, the beamemitted from the electron gun is deflected toward said direction,thereby preventing incidence to the target from being carried out atright angles. In the invention, there is provided the magneticgenerating means 32 for the scanning section to cause the leakagemagnetic field to be reversed in the scanning section near the target,i.e., the reversion of the magnetic field in the scanning section. Thebeam emitted from the electron gun is apparently prevented from beingdeflected because the magnetic lines of force of the two magnetic fieldsare offset by each other, so that the resultant beam vertically impingeson the target. There will now be detailed the aforementionedcharacteristics of the invention referring to FIGS. 2 and 3. The sameparts of FIGS. 2 and 3 as those of FIG. 1 are denoted by the samenumerals and description thereof is omitted. The magnetic lines of forceof a magnetic field formed by the coil 21 extend outwardly from thelongitudinal axis of the pickup tube. The intensity of this magneticfield along the axis is shown by a dotted curve b in FIG. 3. On theother hand, the magnetic lines of force of a magnetic field generated bythe solenoid coil 32 extend inwardly and the intensity of the magneticfield is indicated by a dotted curve c. A solid curve a represents thetrue intensity of the magnetic field along the axis, which is a sum ofsaid two magnetic fields. That is, the curve a is a sum of the curves cand b. The reversing point is shown by a mark p which is movable alongthe axis according to variations in the intensity or distribution of thefield generated by the coil 32. Accordingly, the leakage magnetic fieldin the scanning section near the target may be controlled to obtain adesired value of less than 25 gauss by adjusting the current passingthrough the solenoid coil and/or the locating thereof.

As shown in FIGS. 4 and 5, permanent magnets 40 and 41 may be usedinstead of the solenoid coils 21 and 32 of said device. Both magnets areprepared in the annular form, one magnet 40 being provided with thenorth pole at the inner side and the south pole at the outer sidethereof while the other magnet 41 the south and north poles at the innerand outer sides respectively. The magnetic lines of force areconsequently distributed as shown by the dotted lines of FIG. 4. Theintensities of the magnetic fields along the axis are respectivelyindicated by the dotted curves b, c and solid curve a in FIG. 5, whichrespectively correspond to the three curves in FIG. 3.

The image pickup device using a permanent magnet displays an excellentedge effect by means of controlling the intensity of black border effectfor a reproduced image picture because it elevates the intensity of amagnetic field in the image section near the target so as to shorten thescanning distance of the secondary electrons from the target.

As mentioned above, the present invention enables the intensity of aleakage magnetic field in the scanning section to be controlled to adesired value by suitably changing the position of the reversing pointthrough adjustment of an additional coil. Further the invention not onlyprevents the occurrence of image shading, for example, parabolic shadingcaused by the axial distortion of an image pickup tube or the deflectionof a magnetic field, but also eliminates irregularities in outputsignals which appear crosswise and lengthwise of a reproduced image.

There will now be described by reference to FIGS. 6 and 7 an intensifiervidicon assembled from a multi-stage type image tube and vidicon, towhich the idea of the present invention is applied.

A multi-stage type image tube 50 and vidicon 51 are connected, asillustrated, by a large number of juxtaposed optical fibers 52 to forman intensifier vidicon. Like those in common use, this tube 50 has aphotoelectric plane 54 mounted on one end of an evacuated container 53and a fluorescent layer or plane 55 provided in the container to face tosaid plane 54. Between these two layers 54 and 55 are juxtaposed dynodes56 at a prescribed space using the known method. Around the tube 50 isdisposed a convergence magnetic coil 57. On the other hand the vidicon51 is provided at one end with a photoelectric layer 58, which isoptically connected to the fluorescent plane 55 by the optical fibersand at the other end with an electron gun assembly 59 for scanning saidphotoelectric layer 58. Further, around the vidicon section of thecontainer is formed a separate magnetic coil 60 from the aforementionedmagnetic coil 57 to converge and deflect electron beams from theassembled electron guns 59.

With a device according to this embodiment having the aforesaidarrangement, the magnetic coil 57 of the multi-stage image tube 50 is sodesigned that a magnetic field along the axis of the tube has a value of250 to 200 gauss units as indicated by the dotted curve d of FIG. 7. Onthe other hand the magnetic coil 60 of the vidicon 51 is so designedthat a magnetic field (denoted by the dotted curve 2 of FIG. 7) alongthe axis of the tube is oriented in the opposite direction to the firstmentioned magnetic field and displays a value of 200 gauss units.Accordingly, the resultant magnetic field (indicated by the solid curvef of FIG. 7) has an intensity of 250 to 300 gauss units in the imagetube section 50 of the container 53 and an intensity of 50 gauss unitsin the vidicon section 51, thus enabling both sections to perform aprescribed operation. In the device described above, a singleimage-converting plane or target may be used instead of assembling thefluorescent layer 55, photoelectric layer 58 and optical fibers 52provided therebetween.

It is generally required for an intensifier vidicon that the magneticfield along the axis displays an intensity of 250 to 300 gauss units inthe section of a multi-stage type image tube and a fairly low intensityof about 50 gauss units in the vidicon section. However, a merecombination of both sections, as is usually the case with the prior artdevice, causes the elevated magnetic field of the image tube section toleak toward the vidicon section, with the result that the magnetic fieldalong the axis of the vidicon section rises beyond gauss units toprevent said vidicon section from carrying out a prescribed operation.If, however, there is applied the fundamental idea embodying the presentinvention of impressing one magnetic field with another reverse field,then it will be possible unfailingly to control the intensity of amagnetic field along the axis of the vidicon section to about 50 gaussunits.

What we claim is:

1. An image pickup tube device comprising an evacuated containerdefining a longitudinal axis, which is divided into a scanning sectionand image section, said scanning section including an electron gunmounted for emitting and electron beam along said axis, focussing meansfor focussing the electron beam from said electron gun, electrostaticmeans for electrostatically deflecting the focussed electron beam, acylindrical electrode mounted coaxially with said electron gun, a fieldmesh electrode for supplying the highest electrical potential to saidelectron beam for making said electron beam parallel to said axis, acollimation lens mounted coaxially with said electrodes and formed bythe electrostatic field of said field mesh electrode, and a targetmounted in close parallel relationship to said field mesh electrode andscanned at a low speed by said electron beam, an image section includinga photoelectron cathode mounted at the other end of said vacuumcontainer and a first magnetic field generator provided outside thecontainer on said image section side for focussingflthe image electronsfrom said cathode on said target, which produces a leakage magneticfield on the axis of the containenon said target, characterized in thatsaid scanning section further includes a second magnetic field generatorto generate a magnetic field which reverses the polarity of the leakagefield produced by said first generator near said target.

2. An image pickup tube according to claim 1 wherein said both magneticfield generators are annular electromagnets.

3. An image pickup tube according to claim 1 wherein said both magneticfield generators are annular permanent magnets.

4. An intensifier vidicon comprising a multi-stage type imagesection anda vidicon section which are provided in a common evacuated container,said image section including a photoelectric layer mounted on one end ofsaid container, a fluorescent layer provided in said container saidphotoelectric layer, a plurality of dynodes disposed between said bothlayers, and a first magnetic field generator for focussing the electronbeams from said photoelectric layer, which produce a leakage magneticfield in the vidicon section; and said vidicon section including animage converting means, an electron gun assembly emitting electron beamsto scan the fluorescent layer of this section and a second magneticfield generator to focus said electron beam, which generates a magneticfield to reverse the polarity of said leakage field.

5. An intensifier vidicon according to claim 4 wherein said imageconverting means comprises of a fluorescent layer, a photoelectric layerand light conductive means provided therebetween.

6. An intensifier vidicon according to claim 5 wherein said lightconductive means comprises of a plurality of optical fibers.

t i i i t

1. An image pickup tube device comprising an evacuated containerdefining a longitudinal axis, which is divided into a scanning sectionand image section, said scanning section including an electron gunmounted for emitting and electron beam along said axis, focussing meansfor focussing the electron beam from said electron gun, electrostaticmeans for electrostatically deflecting the focussed electron beam, acylindrical electrode mounted coaxially with said electron gun, a fieldmesh electrode for supplying the highest electrical potential to saidelectron beam for making said electron beam parallel to said axis, acollimation lens mounted coaxially with said electrodes and formed bythe electrostatic field of said field mesh electrode, and a targetmounted in close parallel relationship to said field mesh electrode andscanned at a low speed by said electron beam, an image section includinga photoelectron cathode mounted at the other end of said vacuumcontainer and a first magnetic field generator provided outside thecontainer on said image section side for focussing the image electronsfrom said cathode on said target, which produces a leakage magneticfield on the axis of the container on said target, characterized in thatsaid scanning section further includes a second magnetic field generatorto generate a magnetic field which reverses the polarity of the leakagefield produced by said first generator near said target.
 2. An imagepickup tube according to claim 1 wherein said both magnetic fieldgenerators are annular electromagnets.
 3. An image pickup tube accordingto claim 1 wherein said both magnetic field generators are annularpermanent magnets.
 4. An intensifier vidicon comprising a multi-stagetype image section and a vidicon section which are provided in a commonevacuated container, said image section including a photoelectric layermounted on one end of said container, a fluorescent layer provided insaid container said photoelectric layer, a plurality of dynodes disposedbetween said both layers, and a first magnetic field generator forfocussing the electron beams from said photoelectric layer, whichproduce a leakage magnetic field in the vidicon section; and saidvidicon section including an image converting means, an electron gunassembly emitting electron beams to scan the fluorescent layer of thissection and a second magnetic field generator to focus said electronbeam, which generates a magnetic field to reverse the polarity of saidleakage field.
 5. An intensifier vidicon according to claim 4 whereinsaid image converting means comprises of a fluorescent layer, aphotoelectric layer and light conductive means provided therebetween. 6.An intensifier vidicon according to claim 5 wherein said lightconductive means comprises of a plurality of optical fibers.